1. Examination of the cellular basis of the autologous mixed lymphocyte reaction and its ontogeny. 2. Examination of the mechanism by which the thymus acts to determine the self-restriction and antigen receptor repertoire of developing lymphocytes. 3. Analysis of the fine specificity of T cell antigen recognition and the influence of major histocompatibility complex (MHC) gene products expressed in the thymus and on antigen presenting cells an antigen recognition in T cell clones and T cell hybridomas. 4. Factors affecting antigen driven lymphokine release in antigen specific T cell clones. 5. Studies on the nature of T cell activation as a function of antigen concentration and MHC gene product concentration.